Many people are concerned about fat levels in their pets. It has been estimated that between 25% and 30% of dogs seen by veterinarians are overweight. Obesity in canines has been linked to many serious health issues including heart disease, diabetes, arthritis, respiratory problems, skeletal stress, gastrointestinal disorders, and skin disorders. These are serious issues, but canine obesity can be difficult to diagnose.
One known method for measuring the body fat of a dog is a “rib check,” which entails running one's hand down the ribs and feeling for excess tissue. Most pet owners do not perform this simple test. Moreover, rib checks are subjective in nature and the accuracy of the test (i.e., the determination of the presence and amount of excess fat) depends largely upon the expertise of the handler. Thus, many pet owners distrust the results of this method, even if performed by an experienced and qualified veterinarian.
Many veterinarians and other pet health professionals, in addition to a rib check, may score a dog's obesity utilizing a body condition chart. This chart provides some uniformity, but the results are essentially the same as those of the rib check.
Another method to measure body fat in dogs is DEXA (dual energy X-ray absorptiometry) analysis. This method entails anesthetizing the dog and performing a 15-minute full body X-ray to determine bone/body density. This method is invasive, time consuming, and expensive. Although the results are very accurate, it is not practical to use such a method in ordinary veterinary check-ups or grooming visits.
In recent years, bioelectric impedance analysis (BIA) has gained acceptance as a method for measuring body fat percentage in humans. Scales have been developed utilizing this technology and are available for consumer purchase. Referring to prior art FIG. 9, BIA utilizes two sets of electrodes 142, 144 and 146, 148 connected to the tissue 150 of a subject 166, one set at each of two separate locations 152, 154. A very small, high frequency electrical current 174 is sent from a sinusoidal constant current source 172 between two outermost electrodes 142, 148, which are current source electrodes. This current is small enough to be harmless and undetectable to the subject. Two inner electrodes 144 and 146 act as detecting electrodes and a high input impedance, phase sensitive voltmeter 178 measures a voltage drop and phase lag due to tissue 150 between the two sets of electrodes 142, 144 and 146, 148. The voltage drop is due to the resistance R of tissue 150 and the phase difference is due to the capacitance C of tissue 150. The combination of these two values yields the total impedance of tissue 150. Fatty tissue will have a higher impedance than lean tissue.
Studies have indicated that BIA theory might also be applied to dogs. However, known studies utilized subcutaneous needles to attach electrodes to dogs in conjunction with general anesthesia. These techniques are highly invasive and quite expensive to perform. Moreover, previous studies have lead at least one researcher to conclude that “[n]o useful correlation between impedance measurements involving one or two limbs and major body components has been demonstrated either in the present study . . . or other studies.” (Burkholder, pp. 202). Burkholder found that legs of dogs (which are not generally areas of fat deposits for canines) typically have ten times more resistance than the torso, making it difficult for BIA devices to distinguish between the desired torso impedance measurement (approximately 100 ohms) and the leg impedance (approximately 1,000 ohms.) Therefore, measurements through the legs were not found to correlate well with body fat.